Publications

In early 2008 ION-GXT completed JavaSPANTM, a regional long-offset, deep crustal, 2-D reconnaissance survey. This survey has imaged stratigraphic thicknesses of up to 5 km of pre-Middle Eocene strata locally reserved in faulted synclines 20-50 km wide below the strong regional angular unconformity. These “synformal keels lie below the known inversion structures, indicating the Eocene extensional basins and Miocene inversions nucleated on the pre-existing structures. Our analysis recognizes a possible Australian provenance of the keel strata. The results of the survey thus support the inference that the East Java Sea is underlain by a composite of continental basement blocks or terranes believed to have been rifted from Australia in the Jurassic and accreted against an arc on the SW flank of Kalimantan in the mid-Cretaceous. The E-W orientation of the better imaged keels may represent the fabric of source terrane as these blocks were plucked from the Australian margin. It is oblique to younger structures such as the NE-trending Masalima and Doang bathymetric troughs which are related to the docking of the exotic basement blocks or to more recent extension. We note that younger and less deeply buried strata in cores of synclines may be unmetamorphosed and may source pre-Tertiaryhydrocarbon systems.